Overview

Chronic lymphocytic leukemia (CLL) is a type of cancer of the blood and bone marrow — the spongy tissue inside bones where blood cells are made.

The term "chronic" in chronic lymphocytic leukemia comes from the fact that it typically progresses more slowly than other types of leukemia. The term "lymphocytic" in chronic lymphocytic leukemia comes from the cells affected by the disease — a group of white blood cells called lymphocytes, which help your body fight infection.

Chronic lymphocytic leukemia most commonly affects older adults. There are treatments to help control the disease.

When to see a doctor

Causes

Doctors aren't certain what starts the process that causes chronic lymphocytic leukemia. What's known is that something happens to cause a genetic mutation in the DNA of blood-producing cells. This mutation causes the blood cells to produce abnormal, ineffective lymphocytes.

Beyond being ineffective, these abnormal lymphocytes continue to live and multiply, when normal lymphocytes would die. The abnormal lymphocytes accumulate in the blood and certain organs, where they cause complications. They may crowd healthy cells out of the bone marrow and interfere with normal blood cell production.

Doctors and researchers are working to understand the exact mechanism that causes chronic lymphocytic leukemia.

Risk factors

Factors that may increase the risk of chronic lymphocytic leukemia include:

Your age. This disease occurs most often in older adults. On average, people diagnosed with chronic lymphocytic leukemia are in their 70s.

Your race. Whites are more likely to develop chronic lymphocytic leukemia than are people of other races.

Family history of blood and bone marrow cancers. A family history of chronic lymphocytic leukemia or other blood and bone marrow cancers may increase your risk.

Exposure to chemicals. Certain herbicides and insecticides, including Agent Orange used during the Vietnam War, have been linked to an increased risk of chronic lymphocytic leukemia.

Complications

Chronic lymphocytic leukemia may cause complications such as:

Frequent infections. People with chronic lymphocytic leukemia may experience frequent infections. In most cases, these infections are common infections of the upper and lower respiratory tract. But sometimes more-serious infections can develop.

A switch to a more aggressive form of cancer. A small number of people with chronic lymphocytic leukemia may develop a more aggressive form of cancer called diffuse large B-cell lymphoma. Doctors sometimes refer to this as Richter's syndrome.

Increased risk of other cancers. People with chronic lymphocytic leukemia have an increased risk of other types of cancer, including skin cancer, such as melanoma, and cancers of the lung and the digestive tract.

Immune system problems. A small number of people with chronic lymphocytic leukemia may develop an immune system problem that causes the disease-fighting cells of the immune system to mistakenly attack the red blood cells or the platelets.

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